Secretory Carcinoma with ETV6-NTRK3 Gene Fusion and Lymph Node Metastasis in Maxillary Gingiva: A Case Report with Pathological and Molecular Correlative Studies.

Secretory carcinoma (SC), also known as mammary analogue secretory carcinoma (MASC), is a rare salivary gland neoplasm with distinctive morphology that harbors a diagnostic ETV6 gene rearrangement. MASC was first described as a type of salivary gland neoplasm in 2010 and resembles breast secretory carcinoma. It is often mistaken for other neoplasms. It usually acts as an indolent tumor but can occasionally behave in an aggressive manner. We present a rare case of a patient with an aggressive SC/MASC of maxillary gingivobuccal sulcus with microcystic, solid and papillary patterns that showed ETV6 gene rearrangement by fluorescence in situ hybridization. Next-generation sequencing revealed t(12;15)(p13;q25) ETV6-NTRK3 translocation. Because SC/MASCs harbor the ETV6-NTRK3 translocation, molecular studies and immunostains are crucial to confirm the diagnosis and direct therapy.

Oropharyngeal cancer outcomes correlate with p16 status, multinucleation and immune infiltration.

Oropharyngeal squamous cell carcinoma (OPSCC), largely fueled by the human papillomavirus (HPV), has a complex biological and immunologic phenotype. Although HPV/p16 status can be used to stratify OPSCC patients as a function of survival, it remains unclear what drives an improved treatment response in HPV-associated OPSCC and whether targetable biomarkers exist that can inform a precision oncology approach. We analyzed OPSCC patients treated between 2000 and 2016 and correlated locoregional control (LRC), disease-free survival (DFS) and overall survival (OS) with conventional clinical parameters, risk parameters generated using deep-learning algorithms trained to quantify tumor-infiltrating lymphocytes (TILs) (OP-TIL) and multinucleated tumor cells (MuNI) and targeted transcriptomics. P16 was a dominant determinant of LRC, DFS and OS, but tobacco exposure, OP-TIL and MuNI risk features correlated with clinical outcomes independent of p16 status and the combination of p16, OP-TIL and MuNI generated a better stratification of OPSCC risk compared to individual parameters. Differential gene expression (DEG) analysis demonstrated overlap between MuNI and OP-TIL and identified genes involved in DNA repair, oxidative stress response and tumor immunity as the most prominent correlates with survival. Alteration of inflammatory/immune pathways correlated strongly with all risk features and oncologic outcomes. This suggests that development of OPSCC consists of an intersection between multiple required and permissive oncogenic and immunologic events which may be mechanistically linked. The strong relationship between tumor immunity and oncologic outcomes in OPSCC regardless of HPV status may provide opportunities for further biomarker development and precision oncology approaches incorporating immune checkpoint inhibitors for maximal anti-tumor efficacy.

Stereotactic Radiosurgery for Carcinoid Brain Metastasis: A Case Report.

Carcinoid brain metastases are extremely rare and are associated with a poor prognosis. Treatment options are variable, ranging from surgery, radiation, or chemotherapy alone or combined. We report on a case of rectal carcinoid metastatic to the cerebellum and review chemotherapeutic regimens for carcinoid tumor treatment, focusing on the potential role of temozolomide or stereotactic radiosurgery.

Swallowing Function in Survivors of Oropharyngeal Cancer Is Associated With Advanced T Classification.

OBJECTIVES: The incidence of oropharyngeal squamous cell carcinoma (OPSCC) is rapidly increasing in the United States. The aim of this study was to characterize the functional status of OPSCC survivors to identify predictors of swallowing dysfunction in this patient population. METHODS: OPSCC survivors (n = 81) treated at the Michael E. DeBakey Veterans Affairs Medical Center between 2005 and 2015 with at least 2 years of clinical follow-up were reviewed. Functional status was ascertained using (1) gastrostomy and tracheostomy placement and retention, (2) gastrostomy use at last follow-up, (3) patient-reported diet, and (4) modified barium swallow. RESULTS: Median follow-up duration was 5.6 years; 67% of patients had ≥10-pack-year tobacco exposure; 96% of tumors for which p16 data were available were p16 positive. At last follow-up, 82% of patients reported a regular diet, and only 9 patients required gastrostomy use. Gastrostomy use at last follow-up was higher in patients with T3 and T4 tumors compared with those with T1 and T2 tumors (P = .01). The relationship between T classification and gastrostomy use persisted even when the analysis was limited to p16+ tumors and p16+ tumors with ≥10-pack-year history of tobacco exposure. CONCLUSIONS: Advanced T classification at presentation is a critical predictor of gastrostomy use in long-term OPSCC survivors irrespective of p16 status or tobacco exposure history. LEVEL OF EVIDENCE: 2b.

Overexpression of Semaphorin-3E enhances pancreatic cancer cell growth and associates with poor patient survival.

Semaphorin-3E (Sema3E) is a member of an axon guidance gene family, and has recently been reported to contribute to tumor progression and metastasis. However, its role in pancreatic cancer is yet unknown and uncharacterized. In this study, we showed that Sema3E is overexpressed in human pancreatic cancer, and that high Sema3E levels are associated with tumor progression and poor survival. Interestingly, we also observed Sema3E expression in the nucleus, even though Sema3E is reported to be a secreted protein. Overexpression of Sema3E in pancreatic cancer cells promoted cell proliferation and migration in vitro, and increased tumor incidence and growth in vivo. Conversely, knockout of Sema3E suppressed cancer cell proliferation and migration in vitro, and reduced tumor incidence and size in vivo. Moreover, Sema3E induced cell proliferation via acting through the MAPK/ERK pathway. Collectively, these results reveal an undiscovered role of Sema3E in promoting pancreatic cancer pathogenesis, suggesting that Sema3E may be a suitable prognostic marker and therapeutic target for pancreatic cancer.

Prognostic Significance of p16 Cellular Localization in Oropharyngeal Squamous Cell Carcinoma.

OBJECTIVE: p16 immunohistochemical expression serves as a surrogate for human papillomavirus (HPV)-positive oropharyngeal squamous cell carcinoma (OPSCC). While HPV-positive OPSCC commonly demonstrates prominent nuclear expression, aberrant cytoplasmic expression has been demonstrated in tobacco-related head and neck cancers. The purpose of this study is to investigate the prognostic significance of p16 cellular localization in OPSCC. METHODS: Retrospective cohort study and immunohistochemical expression analysis of 159 OPSCC patients treated at a tertiary-care Veterans Affairs Medical Center. RESULTS: All patients included in this study were male and the majority had significant tobacco (91%) and alcohol (88%) exposure. Overall, 57% of tumors were p16-positive, 32 (20%) subjects have tumors demonstrating low nuclear/low cytoplasmic (LN/LC) p16 expression, 29 (18%) high nuclear/high cytoplasmic (HN/HC) expression, 25 (16%) high nuclear/low cytoplasmic (HN/LC) expression, and 5 (3%) low nuclear/high cytoplasmic (LN/HC) expression. The 5-year disease-free survival (DFS) for the p16-negative group was 13.7%, compared to p16-positive LN/LC 28.4%, LN/HC 0%, HN/LC 74.7%, and HN/HC 93.1% (p<0.0001). Overall survival for the p16-negative group was 24.2%, compared to p16-positive LN/LC 23.5%, LN/HC 0%, HN/LC 74.2%, and HN/HC 88.7% (p<0.0001). On multivariable analysis, HN/HC and HN/LC expression patterns were associated with a statistically significant decreased risk of recurrence and death compared to p16-negative tumors. CONCLUSIONS: P16 localization has prognostic significance in OPSCC, with high nuclear expression associated with significantly better oncologic outcomes compared to low nuclear expression with high or low cytoplasmic p16 expression. P16 localization may provide additional insight into OPSCC carcinogenesis, particularly in patients with heavy tobacco exposure.

Impact of race on oropharyngeal squamous cell carcinoma presentation and outcomes among veterans.

BACKGROUND: Racial disparities in oropharyngeal squamous cell carcinoma (SCC) have been demonstrated and attributed to differences in human papillomavirus (HPV) status. The purpose of this study was to examine racial disparities in oropharyngeal SCC among veterans. METHODS: Retrospective review of patients with oropharyngeal SCC at a tertiary-care Veterans Affairs (VA) hospital. Adjusted Cox proportional hazards models were conducted to examine the effect of race on oropharyngeal SCC outcomes. RESULTS: Of 158 patients, 126 (79.7%) were white and 32 (20.3%) were African American. No difference in p16 tumor expression was noted between the groups. Five-year disease-free survival (DFS) was 42.6% and 55.1% for African Americans and whites, respectively (p = .372). Five-year overall survival (OS) for African Americans and whites was 54.6% and 51.8%, respectively (p = .768). On multivariate analysis, there was no significant difference in risk of recurrence or death by race. CONCLUSION: Racial disparities are largely ameliorated in patients with oropharyngeal SCC treated within the VA, there were no racial differences in p16 tumor expression, and outcomes remain poor.

Identification of an Association of TNFAIP3 Polymorphisms With Matrix Metalloproteinase Expression in Fibroblasts in an Integrative Study of Systemic Sclerosis-Associated Genetic and Environmental Factors.

OBJECTIVE: Systemic sclerosis (SSc) is a fibrotic disease attributed to both genetic susceptibility and environmental factors. This study was undertaken to investigate the associations between SSc-associated genetic variants and the expression of extracellular matrix (ECM) genes in human fibroblasts stimulated with silica particles in time-course and dose-response experiments. METHODS: A total of 200 fibroblast strains were examined for ECM gene expression after stimulation with silica particles. The fibroblasts were genetically profiled using Immunochip assays and then subjected to whole-genome genotype imputation. Associations of genotypes and gene expression were first analyzed in a Caucasian cohort and then validated in a meta-analysis combining the results from Caucasian, African American, and Hispanic subjects. A linear mixed model for longitudinal data analysis was used to identify genetic variants associated with the expression of ECM genes, and the associations were validated by using a haplotype-based longitudinal association test on regions that included the loci identified. RESULTS: The single-nucleotide polymorphism rs58905141 in TNFAIP3 was consistently associated with time-course and/or dose-response expression of MMP3 and MMP1 in the fibroblasts stimulated with silica particles in both the analysis of Caucasian subjects only and the meta-analysis. Results of the haplotype-based analysis validated the association signals. CONCLUSION: Our findings indicate that a genetic variant of TNFAIP3 is strongly associated with the silica-induced profibrotic response of fibroblasts. In silico functional analysis based on the ENCODE database revealed that rs58905141 might affect the binding activities of the transcription factors for TNFAIP3. This is the first genome-wide study of interactions between genetic and environmental factors in a complex SSc fibroblast model.

Oropharyngeal squamous cell carcinoma in the veteran population: Association with traditional carcinogen exposure and poor clinical outcomes.

BACKGROUND: A significant fraction of oropharyngeal squamous cell carcinoma (SCC) cases is associated with traditional carcinogens; in these patients, treatment response and clinical outcomes remain poor. METHODS: We evaluated patient, tumor, and treatment characteristics for 200 veterans with oropharyngeal SCC treated at the Michael E. DeBakey Veterans Affairs Medical Center (MEDVAMC) between 2000 and 2012. RESULTS: Most patients (77%) were white and heavy smokers. Twenty-seven patients required tracheostomy and 63 required gastrostomy placement during treatment. Overall survival (OS) at 5 years was 40%. Survival was impacted by T classification, treatment intensity, completion of treatment, and p16 tumor status. Almost 30% of patients were unable to complete a treatment regimen consistent with National Comprehensive Cancer Network (NCCN) guidelines. CONCLUSION: Oropharyngeal SCC in veterans is associated with traditional carcinogens and poor clinical outcomes. Despite heavy smoking exposure, p16 tumor status significantly impacts survival. Careful consideration must be given to improving treatment paradigms for this cohort given their limited tolerance for treatment escalation.

Lack of Association of the CD247 SNP rs2056626 with Systemic Sclerosis in Han Chinese.

Systemic sclerosis (SSc) is a complex disease involving multiple genetic factors. A recent genome-wide association study (GWAS) indicated that CD247 was strongly associated with SSc, which was subsequently confirmed in a SSc cohort of European population. However, genetic heterogeneity in different ethnic populations may significantly impact the complex trait of SSc. The studies herein aimed to examine whether the SSc-associated SNP rs2056626 of CD247 identified in Caucasian is also associated with Han Chinese SSc. A Han Chinese cohort consisting of 387 SSc patients and 523 healthy controls were examined in the studies. TaqMan assays were performed to examine the SNP. Exact p-values were obtained (Fisher's test) from 2x2 tables of allele counts and disease status. The results showed that there was no association between rs2056626 of CD247 and SSc or any SSc subtypes of Han Chinese. The negative results are important in understanding genetics of SSc in different ethnic populations, which further suggest complex nature of genetics of SSc.

Association of the HLA-DRB1 with scleroderma in Chinese population.

Multiple alleles of the Human leukocyte antigen (HLA) DRB1 have been strongly associated with systemic sclerosis (SSc) and its clinical or serological subsets. However, the associations vary in different ethnic populations. To define SSc-risk and/or -protective alleles of HLA-DRB1 in Chinese population, we studied a Han Chinese cohort containing 585 patients with SSc and 458 gender-matched, unrelated controls. The HLA-DRB1 genotyping was performed with sequence-based typing method. Exact p-values were obtained (Fisher's test) from 2×2 tables of allele frequency and disease status. The major SSc-risk allele subtypes of HLA-DRB1 are the DRB1*15∶02 and *16∶02 in this Chinese cohort. Particularly, DRB1*15∶02 was most significantly associated with anti-centromere autoantibodies (ACA) positive, and DRB1*16∶02 with anti-topoisomerase I autoantibodies (ATA) positive patients. On the other hand, DRB1*01∶01 and *04∶06 were strong SSc-protective alleles in Chinese, especially in patients who were ACA positive and had diffuse cutaneous SSc (dcSSc), respectively. In addition, DRB1*11 and *07∶01 also showed significant association with SSc as a risk for and protection from SSc, respectively, and which is consistent with the studies of Spanish, US Caucasian and Hispanic populations. DRB1*15 was associated with ATA positive Chinese SSc that is consistent with Black South African and Korean SSc. These findings of HLA-DRB1 alleles in association with Chinese SSc provide the growing knowledge of genetics of SSc, and indicate that the genetic heterogeneity among ethnicities may significantly impact the complex trait of SSc.

A case of unsuspected peritoneal mesothelioma occurring with colonic adenocarcinoma masquerading as peritoneal metastases.

We report a case of synchronous primary colonic adenocarcinoma and malignant mesothelioma. A 61-year-old male presented with a six-month history of fatigue and weight loss. An abdominal computed tomography (CT) scan showed a 5.8 cm partially obstructing mass in the cecum with ascites and peritoneal thickening. A biopsy of the large mass showed an adenocarcinoma. Because the patient was clinically thought to be a T4 colon carcinoma with peritoneal metastatic lesions (M1), prior to initiating chemotherapy, a debulking right hemicolectomy was performed. Resection of the colon and ileum revealed a T3N0 colonic mucinous adenocarcinoma and concurrent diffuse malignant peritoneal mesothelioma. Presenting synchronous colonic and peritoneal mesothelial primary malignancies are exceedingly rare but must be considered to prevent incorrect clinical staging.

Primary splenic angiosarcoma associated with anemia, leukocytosis and thrombocytopenia.

Primary angiosarcoma of the spleen is a rare neoplasm arising from endothelial cells. It is an aggressive neoplasm with a poor prognosis. We report a case of 61-year-old Caucasian man who presented with shortness of breath, anemia, leukocytosis, and thrombocytopenia. Ultrasound Sonogram (US) and Computed Tomography (CT) scans revealed a massively enlarged spleen with numerous enhancing hypodense lesions. The spleen was adherent to the omentum, retroperitoneum, and tail of the pancreas. Image-guided Fine Needle Aspiration (FNA) revealed an atypical spindle cell lesion. Resection of the spleen and attached tail of pancreas was performed. Histological examination and immunohistochemical studies revealed a diffuse vascular malignant neoplasm with features of angiosarcoma. The patient appeared disease free after resection. He died within 5 months of unknown etiology.

Inflammatory cells in tissues of gout patients and their correlations with comorbidities.

BACKGROUND: The major pathological finding of gout is the deposition of monosodium urate monohydrate (MSU) crystals with inflammatory infiltrate in the tissue. There have been many reports of in vitro analysis of inflammatory mechanism and comorbidities in gout. However, the associations of immune response cells and comorbidities of gout have not been well documented. Our studies aimed to examine the immune cell types and quantity in gout tissues, and to define the association of individual cell type with comorbidities. METHODS: Surgically resected or biopsied tissues from 48 patients diagnosed as gout were used for this study. Cell count was performed on Hemotoxylin and Eosin stained sections for macrophages, plasma cells, neutrophils and on immunostained slides for T and B lymphocytes. RESULTS: Hyperlipidemia, hypertension and diabetes mellitus were seen in 70.8%, 87.5% and 37.5% of patients, respectively. There were 35.6% and 37.8% of patients who admitted history of smoking and alcohol intake, respectively. Mean serum uric acid level was 8.5 mg/dl. The average body mass index was 30.1 kg/m(2). H&E stained tissue sections demonstrated the crystalline deposits rimmed by palisading multinucleated giant cells, macrophages, neutrophils, plasma cells, T and B cells. Significant correlations between the clinical features and tissue inflammatory cells were observed in hyperlipidemia with number of T cells (p = 0.0363), hypertension with number of T cells and B cells (p = 0.0138 and 0.0033, respectively), diabetes mellitus with macrophages (p = 0.0016), and uric acid level with giant cells (p = 0.0088). CONCLUSION: Comorbidity factors including hyperlipidemia, hypertension and diabetes are significantly associated with the inflammatory cells in the tissues.

Hemophagocytic lymphohistiocytosis associated with influenza A (H1N1) infection in a patient with chronic lymphocytic leukemia: an autopsy case report and review of the literature.

H1N1 influenza A virus can trigger fatal hemophagocytic lymphohistiocytosis in immunocompromised patients and in immunocompetent hosts, usually children. We present a case of a 50-year-old man with low-burden chronic lymphocytic leukemia who had sudden reactivation of his leukemia triggered by influenza A (H1N1) infection with hemophagocytic lymphohistiocytosis during the 2009 H1N1 pandemic. His rapid course was complicated by acute respiratory distress syndrome with diffuse alveolar damage, a 6-fold rise in lymphocyte count, disseminated intravascular coagulation, and, ultimately, cardiac arrest. Major findings at autopsy included: bilateral H1N1 pneumonitis with diffuse alveolar damage, intra-alveolar pulmonary hemorrhage, pulmonary microthromboemboli, pulmonary hemorrhagic infarction, hemophagocytic lymphohistiocytosis in multiple locations, and diffuse chronic lymphocytic leukemia. Hemophagocytic lymphohistiocytosis is a serious and often fatal condition, which may be primary or secondary. It may be associated with high-grade lymphoproliferative malignancies, especially in patients with therapy-related leukocytopenia, but only rarely is it seen in uncomplicated chronic lymphocytic leukemia. Hemophagocytic lymphohistiocytosis may be triggered by a variety of infections (viral, fungal, bacterial and parasitic), but H1N1 influenza A-associated hemophagocytic lymphohistiocytosis is often rapidly fatal, especially in children. This adult patient's clinical presentation with low tumor burden and leukocytosis is thus unique. We review the recently published autopsy findings in fatal influenza A (H1N1) infection and the association with resultant secondary hemophagocytic lymphohistiocytosis.

Decreased catalytic function with altered sumoylation of DNA topoisomerase I in the nuclei of scleroderma fibroblasts.

INTRODUCTION: Sumoylation is involved in nucleolus-nucleoplasm transport of DNA topoisomerase I (topo I), which may associate with changes of cellular and topo I functions. Skin fibroblasts of patients with systemic sclerosis (SSc) exhibit profibrotic cellular changes. The aims of this study were to examine the catalytic function and sumoylation of topo I in the nuclei of SSc fibroblasts, a major cell type involved in the fibrotic process. METHODS: Eleven pairs of fibroblast strains obtained from nonlesional skin biopsies of SSc patients and age/sex/ethnicity-matched normal controls were examined for catalytic function of nuclear topo I. Immunoprecipitation (IP)-Western blots were used to examine sumoylation of fibroblast topo I. Real-time quantitative RT-PCR was used to measure transcript levels of SUMO1 and COL1A2 in the fibroblasts. RESULTS: Topo I in nuclear extracts of SSc fibroblasts generally showed a significantly lower efficiency than that of normal fibroblasts in relaxing equivalent amounts of supercoiled DNA. Increased sumoylation of topo I was clearly observed in 7 of 11 SSc fibroblast strains. Inhibition of SUMO1 with SUMO1 siRNA improved the catalytic efficiency of topo I in the SSc fibroblasts. In contrast, sumoylation of recombinant topo I proteins reduced their catalytic function. CONCLUSIONS: The catalytic function of topo I was decreased in SSc fibroblasts, to which increased sumoylation of topo I may contribute.

Attenuation of fibrosis in vitro and in vivo with SPARC siRNA.

INTRODUCTION: SPARC is a matricellular protein, which, along with other extracellular matrix components including collagens, is commonly over-expressed in fibrotic diseases. The purpose of this study was to examine whether inhibition of SPARC can regulate collagen expression in vitro and in vivo, and subsequently attenuate fibrotic stimulation by bleomycin in mouse skin and lungs. METHODS: In in vitro studies, skin fibroblasts obtained from a Tgfbr1 knock-in mouse (TBR1CA; Cre-ER) were transfected with SPARC siRNA. Gene and protein expressions of the Col1a2 and the Ctgf were examined by real-time RT-PCR and Western blotting, respectively. In in vivo studies, C57BL/6 mice were induced for skin and lung fibrosis by bleomycin and followed by SPARC siRNA treatment through subcutaneous injection and intratracheal instillation, respectively. The pathological changes of skin and lungs were assessed by hematoxylin and eosin and Masson's trichrome stains. The expression changes of collagen in the tissues were assessed by real-time RT-PCR and non-crosslinked fibrillar collagen content assays. RESULTS: SPARC siRNA significantly reduced gene and protein expression of collagen type 1 in fibroblasts obtained from the TBR1CA; Cre-ER mouse that was induced for constitutively active TGF-beta receptor I. Skin and lung fibrosis induced by bleomycin was markedly reduced by treatment with SPARC siRNA. The anti-fibrotic effect of SPARC siRNA in vivo was accompanied by an inhibition of Ctgf expression in these same tissues. CONCLUSIONS: Specific inhibition of SPARC effectively reduced fibrotic changes in vitro and in vivo. SPARC inhibition may represent a potential therapeutic approach to fibrotic diseases.

Pulmonary artery angiosarcoma: a clinicopathologic and radiological correlation.

A 69-year-old man presented with cough, shortness of breath, and fatigue. He was initially treated for allergies and then for pulmonary embolism. Radiologically, a tumor mass was found to occlude the right pulmonary artery and involve the pulmonary trunk. A right pneumonectomy was performed. Histologically, a cellular malignant spindle and epithelioid tumor with areas of necrosis and brisk mitotic activity was seen. In some areas, the tumor appeared to form vascular channels. Focal osteosarcomatous differentiation was present. Immunohistochemical studies were performed including vimentin, smooth muscle actin, desmin, CD31, CD34, S100, and pan-cytokeratin. The tumor cells were positive for CD31 and vimentin and negative for pan-cytokeratin, CD34, and S100. Two months after surgery, the patient was alive and well.

Cyclooxygenase-2 protein reduces tamoxifen and N-(4-hydroxyphenyl)retinamide inhibitory effects in breast cancer cells.

Approximately 30-40% of estrogen receptor alpha (ERalpha)-positive breast tumors express high levels of the cyclooxygenase-2 (COX-2) protein, and these high levels have been associated with a poorer prognosis in breast cancer patients. We speculate that high levels of COX-2 induce drug resistance in ERalpha-positive breast tumors, thus reducing the survival rate of patients with such tumors. Human breast cancer cell lines that express high levels of COX-2 are generally ERalpha negative. To determine whether COX-2 induces drug resistance, plasmids encoding the COX-2 gene were stably transfected into ERalpha-positive MCF-7 human breast cancer cells (MCF-7/COX-2). MCF-7/COX-2 cells were resistant to the selective estrogen receptor modulator tamoxifen but not to its analog, raloxifene. MCF-7/COX-2 cells were also resistant to the retinoid N-(4-hydroxyphenyl)retinamide (4-HPR) but not to its analog, all-trans retinoic acid. In contrast, the sensitivities of MCF-7/COX-2 cells to doxorubicin and paclitaxel were similar to those of the parental MCF-7 cells. We then determined which COX-2 product, prostaglandin E2 (PGE2) or prostaglandin F2alpha is involved in the COX-2-mediated drug resistance. PGE2, but not PGF2alpha, blocked the antiproliferative effects of tamoxifen and 4-HPR. Agonists that activate PGE2 receptors and their downstream kinase effectors, protein kinases A and C, also blocked the growth inhibitory effects of these drugs. Increased levels of Bcl-2 and Bcl-XL proteins have been reported in mammary tumors of COX-2 transgenic mice and in human colon cancer cell lines that have high levels of COX-2. However, we did not observe any changes in Bcl-2, Bcl-XL, or Bax expression induced by COX-2 or PGE2. Here we report the novel findings that COX-2 uses PGE2 to stimulate the activities of protein kinases A and C to induce selectively tamoxifen and 4-HPR resistance in ERalpha-positive breast cancer cells.